Air Conditioner Capacity: The Reason It’s Measured in Tons

What do you think of when you hear the word “ton?” Most people think of how heavy a ton is: 2,000 pounds. But when we’re talking about air conditioner capacity, a ton means something completely different. A three-ton air conditioner doesn’t actually weigh three tons — can you imagine installing a 6,000-pound air conditioner in your home? The term “three tons” is really just an expression for how much an air conditioner can cool a building in one hour.

So, where did that expression come from? Why do we measure air conditioner capacity in tons? Well, in the 19th century (before air conditioners were invented), people used huge blocks of ice to cool their homes. The ice was harvested from frozen lakes in the wintertime and stored until it was needed in the summertime. It takes about 12,000 BTUs — that’s British Thermal Units (one BTU is the amount of energy needed to heat one pound of water by one degree Fahrenheit) — to melt one ton of ice over the course of 24 hours.

As home-cooling methods switched from old-fashioned ice to more modern air conditioning, like today’s coil models, professionals in the industry continued to measure the amount of heat that an air conditioner can remove from a building in terms of tons of ice. So if you have a three-ton air conditioner, and one ton in HVAC parlance equals 12,000 BTUs, then that air conditioner can remove about 36,000 BTUs of heat from your home in one hour.

Now, if you want to get technical, an estimate of air conditioner capacity can be off by a bit. It’s important to get a load calculation, as well as a Manual S calculation, when you’re trying to figure out what kind of air conditioner capacity you’ll need.

Contact the friendly professionals here at Preferred Air Conditioning & Mechanical, Inc. for more information, whether you’re a first-time buyer or you’re looking to replace an old unit. We’re the leading HVAC contractor in the West Palm Beach area.